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How to time camshafts for ignition stroke?

Discussion in 'Technical and Troubleshooting Torque' started by kaldek, Jul 11, 2005.

  1. OK folks, this is a trick one (for me, anyway).

    On the weekend me and my mate pulled the camshafts off his Spada to clean the camchain tensioners. Now I'm looking at the service manual and it looks pretty good to me on getting it all back together and having the cams timed right.

    Except, how do you know whether you've just put the engine back together so that the spark plug fires on the compression stroke rather than the exhaust stroke? There's no sensor on the camshafts so I can only assume that it employs a "wasted spark" system whereby the spark plugs fire on every crank stroke?

    So is there some magical way that the ignition system knows if the engine is on its compression stroke, or is it indeed just a wasted spark system...

    Any help much appreciated,


  2. wasted spark afaik
  3. Thanks mate, it's good to see someone else thinking the same thing. 'Course, I'll still keep checking but I don't see any other way it could work it out (and the service manual says diddly about it).

    I suppose worst case is the engine just keeps cranking but doesn't fire....and then we pull the whole thing apart again.... heh

  4. I am in awe of your bravery, kaldek, I gave up pulling motors apart when I sold my old Triumph (car), but even on a good day I could never figure out how to get the valve timing right. I used to bolt it all back together and get an auto electrician in to do the black magic stuff!
  5. Ahhh yes, I know how you feel. The trick is to do it on a bike which is only worth 3 grand, when you own two bikes, and a car. That tends to reduce the stress levels and the 'oh crap' factor when things go wrong.

    I actually said to my mate while working on it "Now don't go dropping stuff into the crankcase!", to which I promptly dropped a 10mm socket down the engine and straight into the sump. Meh, it needed an oil change anyway. ;)

    And beers help.

  6. I love that feeling. I once drpped $2.00 worth of changed into an ES300 manifold. while leaning over to cover up the cams with a rag overnight while doing rocker covers. That was fun. :roll:
  7. Only becomes an issue when you have a distributor turning at cam speed that controls the spark. If the spark is triggered by the crank you'll have a wasted spark so no problem, the spark don't know the difference.
  8. Yeah, last night I had a good look a the service manual for my 2002 VFR (since it uses fuel injection) and noticed that it has both a crank position sensor and also a camshaft position sensor. So with those two ticking away it can determine which stroke is compression and fire the ignition accordingly.

    It was good to see that because it showed me what needs to be done in order to have a wasted spark. Ergo, the Spada is wasted spark because it doesn't have anything like that. :)

  9. Ok, assuming the spada is like most other pre FI bikes, you will have to remove the cover over the ignition sender unit on the outside of the crankcase.

    Rotate the motor until the No 1 cyclinder is on TDC and set upt your cams from there.

    It may be wasted spark, because it is a v-twin, but I doubt it.
  10. I've already got the ignition sender cover off, ready to set the timing. The only problem with this unit is of course that it's on the crank, so one revolution of the crank brings the marker back to "T1" but of course whether it's on the compression stroke or the exhaust stroke, is totall up to the cams.

    It has to be a wasted spark system, unless the alignment marks only rotate and half engine speed (i.e. one revolution per two revolutions of the crank). Since the marker is *on* the crank, this isn't possible.

    Keep up the responses though. I'm quite happy for anyone to come in here and slap me down with undisputable fact!

  11. Ok I get where your coming from now.

    Yeah your right. The cams determine which stroke you are on and you set your ignition relative to that (rather the other way round).

    I'm still not sure whether it's wasted spark, because I think the smarts are in the module and the ignition sendor just determines TDC each time around. But as you intimate how does it know whether to lay over or fire?. So maybe you are 100% right.

    I got confused because my understanding of wasted spark was like that of Hardleys, where they fire both cylinders at once. So the spark is being "wasted" into the exhasut but 45 degrees out of phase.
  12. I just spoke to my trusted Mechanic (Ben over at Redwing Honda), and he agrees that it's a wasted spark system.


    P.S. I'm sure some of you may have your own opinions about the quality of Redwing's work but I've personally got no problems with them, so let's not turn this thread into a "I don't like my mechanic" story.